The present invention relates to a loading operation vehicle which can properly set a drive mode at an operating time and a traveling time.
Conventionally, in a loading operation vehicle provided with a plurality of hydraulic pumps, there has been known a technique of selecting a combination obtained by changing an output characteristic of an engine and a cut-off condition of a hydraulic pump step by step in accordance with a magnitude of an operation load so as to improve a specific fuel consumption, and this technique is shown, for example, in Japanese Patent Publication No. 7-103593. FIG. 4 shows a control system diagram of a loading operation vehicle disclosed in the publication mentioned above, and a description will be given below of a prior art with reference to FIG. 4.
An output of an engine 1 is transmitted to a torque converter 2 and a gear unit 3, and the output transmitted to the gear unit 3 drives fixed capacity hydraulic pumps 4 and 5.
An electronically controlled type governor 7 capable of selecting the output characteristic of the engine 1 step by step on the basis of the output signal of a governor controller 6 is attached to the engine 1. The governor controller 6 controls the electronically controlled type governor 7 on the basis of a mode selecting signal from an operating switch 8.
The hydraulic pumps 4 and 5 are connected to a bucket main operating valve 10 and a boom main operating valve 11. These working machine operating valves 10 and 11 respectively drive a bucket cylinder 15 and a boom cylinder 14 in accordance with an operation of a bucket operation pilot valve 12 and a boom operation pilot valve 13.
A main unload valve 16 is provided in a discharge side of the hydraulic pump 4. A pilot unload valve 17 and an electromagnetically switched type pilot cut-off valve 18 are connected to a pilot side of the main unload valve 16.
A discharge side circuit of the hydraulic pump 5 is connected to the,pilot side of the pilot unload valve 17 and is opened and closed due to a discharge pressure thereof. Further, the pilot cut-off valve 18 can freely open and close on the basis of an electric signal from a cut-off valve controller 19.
When setting the operating switch 8 to a mode 1, the governor controller 6 outputs a command to the cut-off valve controller 19 so as to close the pilot cut-off valve 18. Accordingly, the main unload valve 16 is opened and closed only on the basis of the discharge pressure of the hydraulic pump 5.
That is, when the discharge pressure of the hydraulic pump 5 is low, the pilot unload valve 17 is closed, the main unload valve 16 is closed and a discharge fluid of the hydraulic pumps 4 and 5 flows through the cylinders 14 and 15. Further, when the discharge pressure of the hydraulic pump 5 is high, the main unload valve 16 is opened and the discharge fluid in the hydraulic pump 4 is unloaded.
Further, when setting the operating switch 8 to a mode 2, the governor controller 6 outputs a signal to the electronically controlled type governor 7 so as to set the output characteristic of the engine 1 so that the output torque is lower with respect to the same rotational number. At this time, in order to open the pilot cut-off valve 18 at an excavating operation time, the main unload valve 16 is opened and the discharge fluid in the hydraulic pump 4 is unloaded.
Further, in the case of setting the operating switch 8 to a mode 3, the output torque of the engine 1 at the same engine rotational number is further lowered and the pilot cut-off valve 18 is always opened in accordance with a signal from the cut-off valve controller 19, whereby the discharge fluid of the hydraulic pump 4 is unloaded.
As mentioned above, in accordance with the conventional art, the specific fuel consumption at the operating time is reduced and operability is improved selectively by a combination between the output characteristic of the engine 1 and the cut-off condition of the hydraulic pump 4 in correspondence to the magnitude of the operation load.
However, there are the following problems in the prior art disclosed in Japanese Patent Publication No. 7-103593.
For example, in the case of an operation of throwing a subject mounted in a bucket 20 to a crusher (not shown) or the like provided apart therefrom, it is necessary that the loading operation vehicle travels far away, so that the travel operation occupies a large percentage of all of the operation. Accordingly, since an amount of fuel consumption required for traveling occupies a large percentage of all of the amount of fuel consumption for the operation, it is required to reduce the amount of fuel consumption for the travel operation.
Further, since an operating time for traveling is increased, it is required to improve a driving characteristic during a traveling time and to reduce noise.
On the contrary, the conventional art relates to the structure for effectively loading and excavating and does not solve the problem of reducing the specific fuel consumption during the traveling time. Accordingly, in the case of the operation in which the traveling time is long, there is a problem that the total specific fuel consumption is not improved so much.
Further, the conventional art does not solve the problems of improving the characteristic during the traveling time and reducing noise, and no countermeasure against the requirement mentioned above is applied.
The present invention is made by taking the problem mentioned above into consideration, and an object of the present invention is to provide a loading operation vehicle which can reduce a specific fuel consumption during a traveling time and improve operability including a driving characteristic.
In order to achieve the object mentioned above, in accordance with a first aspect of the present invention, there is provided a loading operation vehicle comprising:
output characteristic changing means for changing an output characteristic of an engine in a plurality of stages;
shift timing changing means for changing a shift timing of an automatic transmission in a plurality of stages;
working machine flow amount changing means for changing a working machine flow amount of a pressurized oil flowing through a working machine actuator in a plurality of stages;
mode setting means for combining the output characteristic of the engine, the shift timing of the automatic transmission and the set value of the working machine flow amount with each other so as to set a plurality of modes; and
mode selecting means for freely selecting from the modes.
In accordance with the first aspect, there are provided a plurality of modes obtained by changing the output characteristic of the engine, the shift timing of the automatic transmission and the working machine flow amount step by step and combining them, and an operator can freely select the modes.
Accordingly, it is possible to select the combination of the output characteristic of the engine, the shift timing and the working machine flow amount in correspondence to a magnitude of a load, a traveling speed and a working speed. That is, it is possible to increase a working amount and perform a heavy load operation, and in the case that the operation is not a very heavy load operation and the operation is not required to be rapidly performed, it is possible to reduce a specific fuel consumption.
For example, by selecting so that the output characteristic of the engine is a characteristic having a high torque and a high rotation in the case that the load is heavy and selecting in an inverse manner in the case of a low load, the operation can be performed at a proper engine output, so that a wasteful fuel consumption is reduced and a specific fuel consumption can be improved.
Further, by changing the shift timing of the automatic transmission, it is possible to reduce the specific fuel consumption not only at a time of excavating and loading operation but also at a time of traveling. For example, if the structure is made such that a shift-up operation is performed at a delayed timing in the case that an acceleration during a time of traveling is required, a rapid acceleration can be performed, so that the operation can be rapidly performed and a follow-up performance of the vehicle with respect to an accelerating work of the operator can be improved. Further, if the structure is made such that the shift-up operation is performed at an early timing, the specific fuel consumption during the time of traveling is reduced and the sound during the time of traveling is reduced.
Further, by selecting the working machine flow amount of the pressurized fluid flowing through the working machine actuator, it is possible to perform the operation at a proper working machine flow amount in correspondence to a required operation speed, so that the specific fuel consumption at a time of operating is improved. For example, in the case of reducing the working time, the working machine flow amount is increased, and in the case that the operation may be slowly performed, the working machine flow amount is reduced, whereby the specific fuel consumption is further reduced.
In accordance with a second aspect of the present invention, there is provided a loading operation vehicle as recited in the first aspect of the present invention, further comprising a mode (H1, H2) in which a working amount at a unit time is preferential and a mode (L1, L2) in which a specific fuel consumption reduction is preferential.
In accordance with the second aspect, when selecting the mode attaching importance to the working amount in the selectable modes described in the first aspect, it is possible to put on a heavy load and the operation can be finished for a short time, so that productivity can be improved.
On the contrary, at a time of operating under a light load and in the case that the working time reduction is not considered to be important, the specific fuel consumption can be reduced by selecting the mode attaching importance to the specific fuel consumption, so that an economical efficiency can be improved. Since objects of the respective modes can be clearly understood, the operator can easily select.
In accordance with a third aspect of the present invention, there is provided a loading operation vehicle as recited in the second aspect, wherein an intermediate mode (S1, S2) suitable for a normal operation is provided between the mode in which the working amount at the unit time is preferential and the mode in which the specific fuel consumption reduction is preferential.
In accordance with the third aspect, since the intermediate mode suitable for the normal operation is provided in addition to the selectable two modes described in the second aspect, it is possible to select in a finer manner, so that the specific fuel consumption can be further reduced and the operability can be further improved.
In accordance with a fourth aspect of the present invention, there is provided a loading operation vehicle as recited in the first aspect, wherein the output characteristic changing means is an electronic governor for controlling a fuel injection so as to change the output characteristic of the engine in a plurality of stages in accordance with a command of the mode setting means.
Further, in accordance with a fifth aspect of the present invention, there is provided a loading operation vehicle as recited in the first aspect, wherein the output characteristic changing means is an accelerator cylinder for controlling a maximum pedaling angle of an accelerator pedal so as to change the output characteristic of the engine in a plurality of stages in accordance with a command of the mode setting means.
In accordance with the fourth aspect, since the output characteristic changing means is particularly set to the electronic governor for controlling the fuel injection, the operations and effects as described in the first aspect can be obtained.
In accordance with the fifth aspect, since the output characteristic changing means is set to the accelerator cylinder for controlling the maximum pedaling angle of the accelerator pedal, it is possible to control the engine output only by a hydraulic circuit without using a complex electronic circuit such as an electronic governor or the like and no undesirable torque is generated, so that the specific fuel consumption can be further reduced.
In accordance with a sixth aspect of the present invention, there is provided a loading operation vehicle as recited in the first aspect, wherein the working machine flow amount changing means is a cut-off circuit for unloading a discharge fluid in a switching pump so as to change the working machine flow amount of the pressurized fluid flowing through the working machine actuator in a plurality of stages in accordance with a command of the mode setting means.
Further, in accordance with a seventh aspect of the prevent invention, there is provided a loading operation vehicle as recited in the first aspect, wherein the working machine flow amount changing means is a capacity changing circuit for changing a capacity of a variable working machine pump so as to change the working machine flow amount of the pressurized fluid flowing through the working machine actuator in a plurality of stages in accordance with a command of the mode setting means.
In accordance with the sixth aspect, since the working machine flow amount changing means is particularly set to the cut-off circuit for unloading the discharge fluid in the switching pump, the operations and effects as describe in the first aspect can be obtained.
In accordance with the seventh aspect, since the working machine flow amount changing means is set to the capacity changing circuit for changing the capacity of the variable working machine pump, the switching pump is not required. Further, since it is possible to set a fine capacity by changing an angle of the swash plate of the variable working machine pump, it is possible to further reduce a specific fuel ratio and further improve operability.